Laser Design Engineer; Epi​/Device

CScale is a startup backed by Sutter Hill Ventures and Atreides Capital - headquartered in Palo Alto, CA. Our executive team has a demonstrated track record of building and scaling category-defining semiconductor and infrastructure businesses at companies like Broadcom, Lumentum, Tesla, Apple, Samsung, Intel, and VMware.

CScale is developing next-generation optical semiconductor solutions for the AI infrastructure market, focused on enabling true “scale-up” architectures. Our mission is to replace traditional copper interconnects with advanced fiber-optic technologies that overcome the limitations of existing optics solutions and architectures.

At the core of our technology is a high-density III-V laser array — a critical integrated component in our broader optical system — designed for high-volume deployment in AI infrastructure. We are seeking a Senior Laser Design Engineer to own device design and simulation for this laser array, working in a small, cross-functional team where individual contributions are highly visible and directly shape product outcomes.

This role spans the full vertical of laser device design — from active region and heterostructure engineering through waveguide, cavity, and grating simulation for single-frequency laser architectures, as well as electroabsorption modulator design for integrated photonic products. The designs produced in this role must be manufacturable, process-tolerant, and optimized for yield and consistency across production volumes — not just peak performance on a best-case die.

In a fabless environment, simulation is the primary design tool and the foundry interface is the execution path; this engineer must be fluent in both. The right candidate brings deep device physics knowledge across multiple laser and modulator architectures and the practical judgment to make design decisions that survive contact with a real foundry process.

• Design and optimize III-V heterostructures and multi-quantum well (MQW) active regions for laser, SOA, and electroabsorption modulator applications, with explicit consideration of growth tolerance, process variation, and production yield; develop and maintain active region simulation models using commercial tools (e.g., band structure solvers, 1-D optical confinement solvers, traveling wave laser models).
• Simulate and optimize laser waveguide geometry, optical confinement factor, far-field profiles, and cavity design parameters for manufacturability; perform grating simulation for DFB and D  structures including coupling coefficient, stopband, and SMSR — with design margins appropriate for high-volume foundry execution, not worst-case lab conditions.
• Balance output power, threshold current, slope efficiency, SMSR, and linewidth across the full operating envelope — including temperature range and target wavelength window — for production laser devices (DFB, D , and related single-frequency architectures); design for specification compliance across all operating conditions, not only at nominal temperature and center wavelength.
• Design and simulate electroabsorption modulator (EAM) structures — including quantum-confined Stark effect active regions, waveguide integration, and modulation bandwidth — for integrated and stand-alone modulator products; account for the interplay between absorber bias, extinction ratio, insertion loss, and chirp in the context of real driver circuit constraints.
• Serve as the primary technical interface to epitaxy foundry partners: specify growth recipes, review and approve process travelers, evaluate growth run results, and drive resolution of material quality issues.
• Define and execute epitaxial qualification protocols — photoluminescence (PL), X-ray diffraction (XRD), and…